Generally, a liquid crystal panel is composed of a color filter substrate (Color Filter, CF), a TFT array substrate (Thin Film Transistor, TFT), liquid crystal molecules (Liquid Crystal, LC), and a sealant. The working principle is that the liquid crystal molecules are controlled to change directions by applying power to the TFT substrate so that the lights from the backlight module are refracted to form the images.
During the preparation of the color filter substrate and the array substrate, it is necessary to coat the alignment agent thereon, such as the commonly used polyimide, and then the pretilt angle is further formed by rubbing or photo-etching, and thereby the liquid crystal molecules have a bearing angle.
Generally, during the process of coating a polyimide solution, first, the polyimide solution is respectively inkjet-printed onto the array substrate and the color filter substrate; next, the polyimide solution on the substrates are pre-cured for removing the solvent to uniformly form a thin film for preventing the polyimide film from the influence of the rest solvents; then, the thin film is cured to cyclize the polyamic acid (PAA) to form the polyimide film (PI), and ensure the uniformity of the film thickness to prevent mura from occurring.
As shown in FIG. 1, the array substrate 01 or the color filter substrate is coated with an alignment solution, such as a polyimide solution, and a PI film 02 is formed in accordance with a predetermined pattern. However, the positions located at the transfer portions (Au transfer pad) 03 on the array substrate 01 and the positions corresponding to the transfer portions on the color filter substrate do not need to be covered with the PI film. As shown in FIGS. 2 and 3, the PI films often have uneven and irregular thicknesses appearing around a boundary of A-A′, which results in unevenness of the image display and light leakage.
As mentioned above, the design of an alignment film with an even thickness has become a major direction to develop liquid crystal display devices. Therefore, it is necessary to provide a method of manufacturing an alignment film to solve the problems existing in the conventional technology, as described above.